MIT licence and perpetual licence: the difference
Software licences in plain words: what an MIT licence lets you do, what a perpetual licence lets you do, and where the two differ.
Two phrases turn up constantly in searches for business software you install yourself: MIT licence and perpetual licence. They get treated as near synonyms, because both sound like freedom compared with a subscription. They are not synonyms at all, and the difference is about redistribution rather than about price.
Nothing here is legal advice, and nothing on this page tells you what your position is. It describes in plain words what each arrangement typically lets a holder do, which is a question of reading the text you were given.
What an MIT licence typically lets you do
The MIT licence is short -- a paragraph of permissions and a paragraph disclaiming warranties -- and its permissions are broad. A holder can use the software, copy it, change it, combine it with other code, publish it, distribute it, grant sublicences, and sell copies of it.
The one condition attached is small and easy to miss: the copyright notice and the licence text travel with the copy. Ship the software on, and that notice goes with it.
What comes with that breadth is the other paragraph. MIT-licensed software is provided as is, with warranties disclaimed, and nobody undertakes to fix anything. In practice the support you get is the support the project's maintainers feel like providing, which for a healthy project is a great deal and for an abandoned one is nothing.
What a perpetual licence typically lets you do
A perpetual licence is a permission that does not expire. You pay once and may keep using that software for as long as you like -- which is the property people are usually reaching for when they type the phrase.
What it does not typically include is the right to pass the software on. This store's own single licence is a concrete example, and its terms are printed on every product page rather than hidden in a document: it grants installation on one domain or subdomain you own or operate, the full source to read and change however you like for that installation, commercial use including client work, and re-download of the current build from your buyer portal. It excludes reselling, redistributing or sublicensing the source, offering the software to other people as a hosted service, and a second site or an installation handed to a client as theirs -- that last one being what the extended tier covers.
Read those two lists together and the shape is clear. MIT gives away redistribution and gives up any promise of maintenance. A perpetual licence keeps redistribution and usually comes with a maintained build and somewhere to download it from.
The question that actually decides it
Not which licence is better, but what are you going to do with the copy.
Running your own business on it. Both work. The perpetual licence usually arrives finished and maintained; the MIT project arrives as whatever its community has built.
Building it into a product you sell. MIT permits this; a typical perpetual licence does not. This is the fork in the road, and it is the one people discover late.
Handing an installation to a client as theirs. MIT permits it; here that is a different tier, and the product pages say so.
Wanting somebody to be responsible when it breaks. Neither licence creates an obligation by itself. What matters is whether anyone is actively maintaining the thing, and that is a question about the project rather than about the text.
Wanting the software to outlive its author. Both handle this, differently. MIT means anybody can fork it. A perpetual licence with the source included means your copy keeps working and you can change it, even if you cannot pass it on.
The one thing to check in any licence
Whatever it is called, find the answers to four questions in the text itself: how many installations it covers, whether the source comes with it, whether you may pass it on, and what happens when the seller stops trading. Every honest licence answers all four somewhere. This store answers them on each product page and in its legal terms, and the same four questions are the right ones to ask of any project or vendor.
Questions people ask
Is open source always cheaper? Licence cost is one line of the total. Your own time installing, updating and fixing is the other, and for some teams it is the larger one. Neither answer is universal.
Can I resell software I bought under a perpetual licence? Typically not, and here specifically not -- reselling, redistributing and sublicensing the source are excluded, and offering it as a hosted service to other people is excluded too. The text is on the product page.
Does a perpetual licence mean free updates forever? Not by itself. It means the permission to use does not expire. What you get by way of new builds is a separate matter, stated separately; here it is re-download of the current build from your buyer portal.
Where to look next
The licence terms for each tier are printed on the product pages themselves -- Slotly is one, and every other product carries the same structure -- and the store's legal terms hold the rest. For what the subscription alternative costs across a planning horizon, read the observatory: each figure is quoted verbatim beside the date it was read and a link to the page it came from. Prices are on the observatory; read them on the date shown there.
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